I don't know much more than high school chemistry and I was wondering if this set up would work. http://i27.tinypic.com/vdnyv.jpg

It should. Spl1ff actually posted that on post 13 of this thread: https://www.totse.com/community/showthread.php?t=2120181&highlight=nitrous+oxide

Is there a safer alternative to using Ammonium nitrate?

I'd watch out for suck-back action. Can you imagine all of that base getting sucked back into that flask full of HCl? catastrophe begging to take place.

^ invest in 'ONE WAY VALVES' - eliminates suckback or use an empty in-line flask to catch any suck back etc etc